Fabrication and Characterization of Porous Catalyst Support by Gel Casting

Abstract

Porous Catalyst-support were produced from boehmite (AlO(OH)) with the help of Gel casting, where cast samples were dried by i) Conventional method (air drying), ii) Freeze drying (lyophilizing) prior to heat-treatment. Without the addition of solidifying agent (Calcium phosphate), there has been 55% total porosity for Conventionally prepared samples. Secondly, Ca3(PO4)2 as a solidifier was added into the above-mentioned batch prior to gel formation. Gel was casted in the cylindrical mould and the casted samples were undergone drying by both air drying and freeze drying. The Heat treatment made the samples dehydrated and gets transformed into γ-alumina. Both the amount of pore former and solid loading of boehmite was optimized after noticing apparent porosity and mechanical strength. 75% porosity was obtained from the heat-treated sample after conventional drying method with glycerol at 6 hours soaking time. Those samples showed the surface area as 319m2/gm. Freeze drying produced up to 84% porosity after heat-treatment ( at 500 °C with soaking time =6 hours), with the measured surface area is 287m2/g. The microstructural study revealed that there was a higher percentage of pore volume. Higher soaking time(8hours) did lead to the formation of crack into the samples, hence, maximum soaking time was limited to 6 hours. Overall 75% porosity was achieved by Conventional drying method and 84% from Freeze drying method to develop γ-aluminawhich is aimed at Catalytic applications.